They braved storms, pirates and boredom; sailed 60,006 kilometers; crossed oceans; and stopped at dozens of ports around the world. And Friday, having circumnavigated the world, the Turanor PlanetSolar and its crew arrived back in Monaco, where their journey had begun in September 2010.

Shaped like a sleek spaceship, 31 meters, or about 102 feet, long and covered with 537 square meters, or 5,780 square feet, of solar panels, the PlanetSolar is the brainchild of Raphaël Domjan, who decided in 2004 to try to demonstrate the tremendous potential of solar technology by sailing a boat around the world using nothing but energy from the sun.

It took years of fund-raising, research and feasibility studies, 64,000 hours of construction and 585 days of sailing, but he made his point: The PlanetSolar glided effortlessly into Port Hercules amid cheering crowds and booming ships’ sirens. A gala dinner followed, as did a light show powered by the remaining solar energy stored in the PlanetSolar’s batteries.

“People did not think that it was possible to do, but we have demonstrated for the first time that you can do it — you can travel around the world in a boat using solar technology alone,” Mr. Domjan, a former ambulance driver, mountain guide and rescue specialist, said by telephone last week, as the PlanetSolar was in the home stretch of its unprecedented trip. “That was the point: to spread the message, to politicians and to the business world, that if we can do this, if we can power a boat around the world, then we can use solar energy much more in other ways, too.”

Mr. Domjan had the financial support of Immo Ströher, a German businessman and a passionate advocate of solar energy, as well as other sponsors and partners. The project team, consisting of an onboard crew of five and a dozen others on shore who handled planning, marketing and communications and offered scientific advice, has taken its message literally around the world.

From Monaco, the PlanetSolar travelled to Miami and on to Cancún, Mexico, in time for the international climate change conference in December 2010. After traveling through the Panama Canal, the ship continued on to the Galápagos Islands, Australia, Hong Kong, India and Abu Dhabi and then through the Suez Canal and back into the Mediterranean Sea.

Along the way the team met ministers and presidents, children and fishermen. Ninety-nine point nine percent of the time, Mr. Domjan said, people were curious and welcoming. In Sri Lanka, he said, fishermen offered them some of their meager catch as a gift.

One of the highlights of the trip, he said, was the sight of land — the islands of French Polynesia — after weeks of journeying across the monotonous open sea from the Galápagos Islands.

“You see nothing for 30 days — you’re in the middle of nowhere, you feel like you are in outer space,” said Mr. Domjan, a native of Switzerland. “And then suddenly you see mountains — it was amazing, a very strong moment.”

The low point involved technical problems with the ship’s propeller when a storm hit them off Abu Dhabi. (The solar technology that powered the boat, however, worked without a hitch throughout the entire trip, Mr. Domjan said.) The Gulf of Aden, where piracy is a serious problem, was the most challenging passage, putting the crew and security experts who joined them for that segment of the trip constantly on edge.

Now that the sheer romance and adventure of it all is over, the focus will be on getting out the message that modern solar technology has proved itself in the face of tough, stressful conditions as the PlanetSolar sailed around the world.

A separate project to fly an aircraft around the world on solar power is also under way; the Solar Impulse, in development since 2005, has made several flights already, and an around-the-world journey is scheduled for 2014.

Both projects are aimed at advancing the cause of renewable energies in the face of climate change rather than being commercially viable enterprises.

And solar energy will probably never be the sole source of power for large vessels like container ships and tankers.

Still, improvements in the efficiency of solar panels and batteries in the past few years mean that ships like the PlanetSolar, if built today, would be far more efficient and cheaper. Experts believe that opens up many more potential uses for the technology.

At the same time, the PlanetSolar and Solar Impulse projects come at a time when many industries are more open to alternative energy than ever before.

The price of fuel for ships, just like those for gasoline used in cars and jet fuel for aircraft, has jumped during the past few years, prompting engineers to rethink hull and engine designs, and managers to mandate lower, less fuel-guzzling speeds for their ships.

“The whole concept of energy efficiency is right at the top of everyone’s agenda,” said Arthur Bowring, managing director of the Hong Kong Shipowners Association, one of the largest groups of its kind. “Ship owners want to see alternatives, and the data that backs them up — and the PlanetSolar has shown that solar is viable.”

For now, once the post-return parties, interviews and speeches have died down, Mr. Domjan is planning some time off to recharge his own batteries — which, he said, are “pretty empty” right now.

But then it is back to work — land-bound this time — spreading the solar message and the story of the PlanetSolar’s trip and experiences.

“We’ve shown that the technology works — it can even be improved,” Mr. Domjan said. “What we need to do now is to change people’s minds — that is the second stage of this whole project.”

The plan is to have a book and a 52-minute documentary film, in French, English and German, ready by Sept. 27, exactly two years after the PlanetSolar set off on its voyage around the world.